Explosive device



July 12, 1960 A, R, ELY Em 2,944,485

EXPLOSIVE DEVICE Filed Oct. 5, 1955 V rA/vE/vroes AZEEZT Q. ELY

JACK 0 H45 5 B08527 W LAWRENCE AGENT.

2 Sheets-Sheet 2 INVENTOES: ALB/527' l2 ELY JACK 0. HAYES EOEEET Ml.ZAWEENCE AG E N T.

July 12, 1960 A. R. ELY ET AL EXPLOSIVE DEVICE Filed Oct. 5, 1955 4Claims. (Cl. 10224) This invention relates to animproved means ofpriming relatively insensitive'explosives and blasting agents and moreparticularly to improved primer units and primed blasting assemblies. f

In recent years the relatively insensitive blasting explosives,consisting primarily of ammonium nitrate and various sensitizingmaterials, have enjoyed an ever increasing popularity. Once theseinsensitive explosive compositions are brought to detonation, they shootat a high rate and in manycas'es may be substituted inblast ingoperations for the blasting cap sensitive type ofexplosive formerlyused. a The relatively insensitive powders, however, haveseveralunfortunate characteristics WhiChmHSt be overcome to render their use-completelysatisfactory. In the first place, the insensitivity of thesecompositions-requiresan initiating means considerably stronger than thecommercially available blasting cap. The art has, therefore,

found it necessary to employ special priming means such as extra largebooster caps containing sizable-base charges of sensitiveexplosive suchas pentaerythritol tetranitrate 'or RDX (cyclotrimethylenetrinitramine).

Alternatively, cartridges of eap-sensitive explosive have been employedto initiate the main charge of cap-insensitive explosive. Many of thesecap-sensitive compositions are also of very high ammonium nitratecontent. Metal cansfilled with-TNT-havealsobeen used as primers 'forinsensitive compositions.- *These cans are normally employed to pnmeinsensiuve compositions also packed' in metalcansand are sometimesequipped withthr'ead-s for engagement with ,firatingfthreads on thecartridges. Such structures are undesirablyexpensive.

. "of th'ese insensitive compositions are by their very .nature'highlyhygroscopic and extreme precautions must be taken to prevent the entryof water andeven moisture into. the cartridge prior to detonation. Someof; the cartridgesrof insensitive explosive havebeenfurnished withdetonator. wells 'to receive booster caps. It is common practice,moieover, to actually: slit the'sid'e of cartridges and insert thebooster cap oriother priming means into the interior .of'thecharg,'-Jdespite the possibility that severe moisture or waterconditions will be' met. prior to detonation of the charge sT-hejprovision of defonator wells or tunnels for detonatin'gfuse'addsbothto the expense of the production ,oflthe individual cartridge; and,what is probably even"niore. important," provides additional' jointsbetween materials of construction where leaks. can occur with resultantentry of moisture or water intoacartridge. I". i p i It will,therefore,"beseen that a really satisfactory priming means for theinsensitive hygroscopic blasting compositions is not presentlyavailable. Not only do 'mostxof the present methodsof priming andcartridging invite the entry ofwater and moisture but, moreover,additional components in the form of powderpun'ches,

boosters, extrapriming cartridges and the like are necessary.

2,944 485 Patented July 12,1960

Now in accordance with the present invention, priming means; forwater-sensitive, cap-insensitive explosives have been discovered whichare themselves readily initiated -by a blasting cap or a detonative fusesuch as Primacord and furthermore give positive initiation toinsensitive powders without in any way endangering the waterproofing ofthe cartridge in which the composition is furnished.

Generally described, in its simplest embodiment, the present inventionis a primer unit for detonating explosives and adapted to being attachedto blasting cartridges which comprises a container, a solid charge ofblasting cap and detonative fuse sensitive explosive'compositiondisposed within the container, and a passageway for an initiating meanspassing through a wall of the container and extending at least partiallythrough the charge, said charge comprising the polymerization product ofa mixture of polymerizable, normally liquid vinyl material andsufficient blasting cap-sensitive, nonaromatic, crystalline highexplosive to render the solid charge atleast as sensitive to detonationas a polymerization product containing 60% pentaerythritol tetranitrateand 40% polymer or 40% of a combination of polymer and plasticizer. Ifthe passageway extends onlypart'way through the priming charge, a wellis thus provided for a blasting cap. On the other hand, if thepassageway extends completely through the charge and its container,detonative fuse, such as 'Prim'acord, also may be readily threadedthrough the passageway. In either event, the initiating means is inclose propagating relationship with the priming charge. Thewell orpassageway may belined with metal, paper or plastic and the like," ormay beunlined as may be desired, Theprimingchargesthemselvesmaybeprepared from any polymerizable-ormonomericvinylsubstance in admixture withgthe desired amount of crystalline highexplosive. 'The invention is limited to the vinyl type of polymerizablesubstance-since these materials polymerize readily at low temperature bylinear addition and/or crosslinking and withoutithe generation ofundesired gaseous or liquid by-products as contrasted with materialssuch as urea-formaldehyde or phenol-formaldehyde resins which cure by acondensation reaction, give ofi the undesired gaseous or liquidby-pr'oducts, and require curing temperatures which are generally unsafein the presence of crystalline high explosives such as pentaerythritoltetranitrate and the like.

In accordance with other and more specific embodiments of the invention,the primer unit may be placed within a sleeve which in the field may bereadily slipped over the end 'of=.an explosive cartridge to bring theprimer unit into priming and propagating'relationship with the main'explosive charge'in the cartridge. The priming unit may be sealed inplace in the sleeve by adhesive,

wax-like substances which will provide strength and waterproofing to thestructure. As a further alternative,

the priming unit of the invention may be employed 'between explosivecartridges in blasting assemblies built up by'use of connecting sleeveswhich extend across the ends "of the explosive cartridges. and theprimer unit disposed therebetween.. r I i V r Having generally describedthe invention, more specific description of several embodiments ispresented with reference to the accompanying drawings, .inwhicli likesymbols refer to like structural elements. In--Figs. 1 through 4, apreferred embodiment of the basic'primer structure is shown. In Figs. 5,6 and 7 partsectional part elevational views of more specificembodiments of the inventionare shown. In Fig. 8 another embodiment of apriming unit is shown. i

"In Figs. 1. through 4, a basic primer structure is illustrated in whicha cylindrical paper'tube 11 is provided with two,slots"13 disposedatpoints 18,0 apart on the cylinder. A paper cover 12 is press fittedover each end of the cylinder 11 and an aluminum tube 14 passes throughslots 13 and extends beyond the cylinder wall 13. A solid block ofcap-sensitive explosive composition 15 is disposed within the container10 and about the tube 14. The unit shown is preferably prepared byinitially placing one cover 12 in position on the end of the cylinder 11opposite the slots 13. The aluminum tube 14 is then placed in the slots13 and allowed to extend the desired distance on either side of thecylinder 11. The explosive composition 15 is then prepared by admixing79.5 parts of pentaerythritol tetranitrate, 2.5 parts ofdiallylphthalate, 17.7 parts of styrene-glycol maleate (70/ 30) and .3part of methyl ethyl ketone peroxide. This mixture is a stiff, moldableplastic mass. The composition is loaded into the cylinder 11 and packedaround the aluminum tube 14. The second cover 12 is then placed inposition as shown in Fig. 2 and the entire unit is maintained at acuring temperature, preferably at a temperature of about 15 to 50 C.,until a solid polymerization product is obtained.

In the structure described, the primer is suitably initiated by passinga detonative fuse such as Primacord through the tube 14. The primer unit10 may be attached to the explosive cartridge or charge to be initiatedby any suitable means, particular embodiments of which will besubsequently described. The tube 14 may be replaced by one or moreinitiator wells if desired and initiation may be obtained through theaction of an ordinary blasting cap instead of detonativerfuse.

In Fig; is shown a preferred embodiment of a more specific priming unitwhich may be readily attached to an explosive cartridge without in anyway defacing the cartridge or altering its Waterproof characteristics. Apriming unit. similar to that described in Figs. 1 through 4 isdiametrically centered within a spirally wrapped paper sleeve 50 andadjacent one end of the sleeve. The aluminum tube 14 extends through thewalls of the sleeve at points 180 apart and is secured at each end tothe sleevezby being flared as at 51. The end of the sleeve 50 is crimpedinwardly to form a fluted crimp 52 which in this instance substantiallycloses one end of the sleeve leaving only a small orifice 53 in thecenter of the crimp 52. A body of adhesive, waxlike sealing compound 54is disposed in a continuous form about the unit 10 within the sleeve andabove and below the fluted crimp 52 to provide a rigid and waterproofseal about the unit '10 and in the end of the sleeve 50. An explosivecartridge 55 with an external diameter substantially the same as theinternal diameter of the sleeve 50 is disposed in snug slidablerelationship within the sleeve 50 with the lower surface of the primerunit10 in juxtaposition to the upper surface of the cartridge.

In Fig. 6, a primer unit 10 equipped. with tube 14 is diametricallycentered Within a sleeve 60 atapproxirnately the mid point of thesleeve. The ends of the tube 14 are again secured to the outer surfaces.of the tube 60 by being flared as at 61. An explosive cartridge 62having an external diameter substantially the same as the internaldiameter of the sleeve 60 is inserted into each end of the sleeve 60until the ends of the cartridges 62 are in juxtaposition to the upperand lower surfaces of the primer unit 10. The ends of the cartridges aresealed by means of a fluted crimp 63 and a continuous layer '64 ofadhesive, waxlike material is disposed above and below the crimp andinthe orifice formed in'thecenter of the crimp 63. V p

In Fig. 7, a primer unit similar to that shown in Figs. 1 4 and employedin Figs. 5 and 6 is disposed substantially concentrically within asleeve 70 and at substantially the end of the sleeve. The ends of thetube 14 pass through the wall of the sleeve 70 at points 180 apart andare secured in place by means of, grommets 71. A continuous body 72 ofadhesive, waxlike. compound is disposed about the container 11 in thetube 14 forming a rigid and waterproof seal adjacent the end of the tube70. An explosive cartridge 73 having an outside diameter substantiallyequal to the inside diameter of the sleeve 70 is disposed Within thesleeve 70 with the upper end of the cartridge being in juxtaposition tothe lower surface of the priming unit 10. v H

In Fig. 8, a printingunit similar 'to that shown in Figs. 1 through 4,except for having a detonator well 84 extending downwardly into theinterior ofthe unit, is disposed between two explosive cartridges 81 inend to end abutting relationship. A connecting sleeve 82 is disposedabout the ends of the cartridges 81 and the priming unit 80 to form arigid connecting explosive column. A blasting cap 83 is disposed in thewell 84. Lead wires 85 lead from the blasting cap, between the cartridge81 and the sleeve 82, and are connected to a power source. The explosiveassembly of Fig. 8 is especially adapted for use in seismic prospectingoperations.

In all of the units shown in Figs. 5, 6, 7 and 8, the sleeves may beadhesively secured to the cartridges. The use of adhesives is normallynot preferred, however, unless the cartridge-primer structure is to bestored, shipped and furnished in the field as a unit.

In the structures of the invention as illustrated by the embodimentsdescribed, it is preferred that the containers for the plastic explosivecomposition and the sleeves employed for attaching the primer units toexplosive cartridges be made from paper, cardboard or other ccllulosicmaterials. However, sleeves, andcontainers for the plastic explosive mayalso be made from metal or plastic. The detonator wells and fuse tubeswhich pass into or through the plastic polymerization product also maybe metal, plastic or paper. The cartridge shells andconnecting sleevesare also preferably made of paper or other cellulosic material, althoughthey too may be made from plastic or metal if desired.

The polymeric binding material acting as a matrix for the particulatehigh explosive will be prepared from mon omeric or further polymerizablevinyl substances which readily form linear or cross-linked type polymersin the presence of a polymerization catalyst at low temperatures. Suchsubstances include the acrylic type-of materials suchv as methyl, ethyland .butyl acrylate, ethyl, methyl, and .butyl methacrylate, and thelike; styrene;. styrene.- polyesters, acrylonitrile and the like.Preferred'styrenepolyesters will contain about -3070% styrene and about70%30% of polyester. The preferred polyesters are the reaction productsof ethylene glycol, diethylene glycol or propylene glycol with maleic,furnaric orphthalic acid. Crosslinking agents such as diallylphthalateand triallyl cyanurate may also be included. Commercial types ofstyrene-polyesters which give' excellent results are Stypol 107E,manufactured by H. H. Robertson (30., Selectron 5003, manufactured byPittsburgh Plate Glass Co., and Vibrin 121, manufactured by NaugatuckChemical Co. The commercial products often contain a polymerizationaccelerator such as cobalt naphthenate. More than one of the above. andequivalent polymerizable materials may be. copolymerized if desired. As.previously mentioned, the materials which harden by condensation typereactions are not operable in the invention since in general theyrequire undesirably high temperatures for the reaction and invariablyevolve undesirable gaseous or liquid by-products which adversely affectthe physical. properties of the final polymerization product..

The priming compositions of the. invention are prepared by admixing theparticulate explosive with the polymerizable material and catalyst andthen curing the mixture to 'otain a solid body. Preferably, the mixturewill be cured its final paper, metal or plastic container. If desired,however, the polymerization products may be formed in special molds andthen loaded into their containers.

The usual polymerization catalysts known and employed by the art for thepolymerization of vinyl type materials may be employed in preparing theexplosive compositions of the invention. Such catalysts include benzoylperoxide, cumene hydroperoxide, methyl ethyl ketone peroxide and thelike. As catalysts, benzoyl peroxide and methyl ethyl ketone peroxideare preferred.

While any blasting cap-sensitive, nonaromatic crystalline high explosiveis operable in preparing the priming charges of the invention, the moresensitive explosive such as pentaerythritol tetranitrarte and RDX(cyclotrimethyl- 'ene trinitramine) are preferred. However, such othermaterials as sucrose octanitrate, lactose octanitrate and mannitolhexanitrate may also be employed. For best rcsults the crystallineexplosive should not contain more than about 1% moisture. Aromaticexplosive compounds are not operable in the invention since the aromaticnucleus inhibits polymerization of the vinyl material and thus preventssatisfactory consolidation of the charge.

It has been found that in order to obtain the desired physical strengththe plastic explosives employed in the primer units of the inventionshould contain at least of polymeric material. The upper limit ofpolymeric material will depend upon the sensitivity desired in thepolymerization product. In general, to be sensitive to Primacord or No.6 Cap, the composition should contain at least 60% of pentaery-thritoltetranitrate or an amount of other crystalline explosive which willresult in a sensitivity equivalent to a composition containing 60% ofpentaerythritol tetranitrate and 40% of polymeric material.

Although the priming units of the invention are primarily intended foruse with the blasting cap or detonative fuse insensitive explosivecompositions, these units may, if desired, be employed with otherexplosive compositions of greater sensitivity where more positivepriming is deemed desirable. For example, they provide an excellentpriming means for gelatinous explosives which are desensitized bypressure. The primers of the invention are relatively unafiected bywater or pressure and have been shot under a pressure of 500 p.s.i. by aNo. 6 Cap after being exposed to a water pressure of 500 p.s.i. for morethan one week. As a result of these properties, the primers of theinvention are already widely used in seismic prospecting operations toinitiate gelatin explosives.

Since the invention as described will be subject to con:

siderable modification by those skilled in the art, it, is intended thatthe invention be limited only by the scope of the appended claims.

What we claim and desire to protect by Letters Patent 1s:

1. A primer unit especially adapted for detonating cylindrical explosivecartridges comprising, in combination, a flat, cylindrical body memberhaving a length substantially less thanits diameter essentiallyconsisting of a covered unitary mass of a fissure-free syntheticwaterproof, self-sustaining, resinous polymerization product containingdispersed therein at least of a particulate, nonaromatic, crystallinehigh explosive, and a longitudinal, substantially imperforate tube toreceive explosive initiating means therein embedded substantially midwayof the length of the flat, cylindrical body member and diametricallyextending entirely through said body member.

2. A primer unit in accordance with claim 1 in which I each end of saidlongitudinal tube passes through and supports a sleeve elementconcentrically positioned about the primer unit.

3. A primer unit in accordance with claim 2 in which the primer unit isrigidly secured to the sleeve element by a sealing compound castthereabout within the sleeve.

4. A primer unit in accordance with claim ,3 in which one end of thesleeve is inwardly crimped over the primer unit and the sealing compoundextends above said crimp.

References Cited in the file of this patent UNITED STATES PATENTS

